To drive a power transistor such as an insulated gate bipolar transistor (IGBT), it is necessary to apply a high voltage of 10 V or more to its gate. Therefore, a gate voltage of the power transistor is often controlled by a high-side transistor and a low-side transistor with high breakdown voltages.
When a transistor driver that drives the high-side transistor and a transistor driver that drives the low-side transistor are activated, malfunction of these transistors may occur if a voltage of an intermediate voltage line between a power supply line on high voltage side and a power supply line on a low voltage side does not appropriately rise. Therefore, appropriate countermeasures to prevent such malfunction are desired.